Support meta and annotation in mcp tools

[luoxiner]

Is your feature request related to a problem? Please describe.

The current MCP Tool model in Nacos does not fully comply with the MCP protocol specification. According to the MCP protocol, Tool objects should support two additional fields:

• _meta: A generic metadata object for storing arbitrary key-value pairs
• annotations: Additional properties describing a Tool to clients (ToolAnnotations)

Without these fields, Nacos cannot store and manage the complete MCP Tool specification, which limits interoperability with MCP-compliant clients and servers.

Describe the solution you'd like

Add support for _meta and annotations fields in the MCP Tool model:

1. Backend Changes:

   • Add _meta field to McpTool.java with proper JSON serialization using @JsonProperty("_meta")
   • Create McpToolAnnotations.java class with the following fields as defined in MCP protocol:
     • title (String): A human-readable title for the tool
     • readOnlyHint (Boolean): If true, the tool does not modify its environment
     • destructiveHint (Boolean): If true, the tool may perform destructive updates
     • idempotentHint (Boolean): If true, repeated calls have no additional effect
     • openWorldHint (Boolean): If true, the tool may interact with external entities
   • Add annotations field to McpTool.java

2. Frontend Changes:

   • Add "Meta" tab in CreateTools dialog with JSON editor for _meta field
   • Add "Annotations" tab in CreateTools dialog with form controls for annotation fields
   • Display _meta and annotations in ShowTools component

Describe alternatives you've considered

1. Store as generic Map<String, Object>: We could store both fields as generic maps, but this would lose type safety for annotations and make frontend form binding more complex.

2. Only support _meta field: We could implement only the _meta field as it's more flexible, but this would still leave Nacos non-compliant with the full MCP Tool specification.

Additional context

MCP Protocol Tool Definition Reference:

{
  "name": "tool_name",
  "description": "Tool description",
  "inputSchema": {...},
  "_meta": {
    "additionalProperties": {},
    "type": "object"
  },
  "annotations": {
    "title": "Human readable title",
    "readOnlyHint": false,
    "destructiveHint": true,
    "idempotentHint": false,
    "openWorldHint": true
  }
}

Note: All properties in annotations are hints and are not guaranteed to provide a faithful description of tool behavior. Clients should never make tool use decisions based on annotations received from untrusted servers.